Animal studies are expensive and time-consuming, and sometimes raise ethical questions. In the past, researchers have often used more animal blood and lives than was necessary. Now there is pressure to reduce the number of animals used in any study, for both ethical and financial reasons.
Research into new medications and treatments for disease requires both preclinical and clinical studies. Preclinical experiments are done both in vivo and in vitro. In vivo means the experiment is done within an animal, such as a mouse. In vitro experimentation is done on Petri dishes or in test tubes. The test tubes come first, but the next step is animal studies if the in vitro observations are promising.
Extracting blood from mice used to require a lot of skill and access to a good vein. In recent years, researchers have been using just one drop of blood, picked up with a capillary tube, about 20 microliters. The capillary tube was applied to filter paper where the blood formed a circle. The card was dried and the circle punched out and analyzed. This method was sensitive to the animal's hematocrit. If the hematocrit is elevated, the blood is more viscous and will not spread well on the filter paper. Therefore the circle will be smaller, causing the drug concentration to be erroneously high. While blood collection in this method is relatively easy, application of the blood to the paper and punching out the circles is labor intensive.
Microsampling is a cutting-edge method that is shifting assumptions about preclinical workflows. The instruments used in this method are smaller, collecting only 10 microliters instead of 20 and shortening the collection time. Instead of using filter paper, the tubes are placed in a tray and frozen. This reduction in the necessary blood volume has allowed scientists to use serial sampling, in which they draw multiple samples from one animal, decreasing the number of animals needed for the experiment. One study went from 64 mice for a traditional large blood volume study to eight mice in the capillary microsampling experiment.
In addition to reducing the number of animals needed, the tiny capillary tubes are cheaper than the larger ones. There is no filter paper needed. The labor involved is also decreased. Capillary microsampling has been shown to be not only an easier and less expensive method of processing blood samples. its results are equivalent to both traditional dried blood spot testing.
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